Here's my BetrayerInsanity take based on The Smile Tapes! ^w^

Lore:

After experiment of the scientists were the patients are going to work on the fungus, and after a week ago, they inhaled the spores and turn them into the smile, and they are being quarantined on the surface of the monsters and the humans to stay inside.

Sans is the victim of inhaling of spore puffing instead of Shaun Gomez, Papyrus was sick and he's worried about him, he saw a mysterious man (Gaster) in his dreams for the past weeks before he's kind of worrying him up, Papyrus was feeling better again before his face wont stop twitching and having a migraine to have a worst one so far, he thought that'll be stress, and he's an agony.

Alphys told him that could be stress and electrolyte imbalance, he tooks some meds and relax before stay hydrated.

Days later, his face hurts and pulling the sides of his mouth up before it's getting hard to blink, the meds don't work and Papyrus passed away after he was just doing fine.

They think the monsters and the humans tells him looking fine recently, he's NOT.

Behind his forced smile, he's suffering, both physically, mentally anguish and rage, and now he's happy and full of energy to feel Gaster's aura to change him to make the better life when whoever was happy.

And he started another havoc to kill and infect thousands more to his mutation, the mutation are, bloodthirsty, inhuman strength, stamina and mana, bulletproof exterior and magic attacks.

UnderTale: Betrayer by Avranik

Undertale: Insanity by UTF

UnderTale: Jester's Demise by me!! ^w^